package acwing;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class ac790 {
    public static void main(String[] args) throws IOException {
        BufferedReader cin = new BufferedReader(new InputStreamReader(System.in));
        double n = Double.parseDouble(cin.readLine());
        double l = -10000, r = 10000;
        while(l - r > 1e-8){
            double mid = (l + r) / 2;
            if(mid * mid * mid < n) l = mid;
            else r = mid;
        }
        System.out.printf("%.6f\n", l);
    }
}
